Signaling optimization method and device

ABSTRACT

Disclosed are a signaling optimization method and device, to resolve a problem of heavy signaling overheads and long data transmission delay when a user equipment (UE) accesses a network side. The method includes: receiving, by the UE, configuration information sent by a first network side device, where the configuration information includes a list, and the list is a cell list or a base station list; and entering, by the UE, an intermediate state according to the configuration information, where the intermediate state means that: when the UE stores context information of the UE, if the UE moves and a cell movement range falls within a coverage area of a cell or a base station included in the list, the UE performs cell reselection according to the list. Embodiments of the present disclosure are applicable to optimization of signaling transmission between the UE and a network side.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2015/072452, filed on Feb. 6, 2015, the disclosure of which ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the communications field, and inparticular, to a signaling optimization method and a device.

BACKGROUND

Long Term Evolution (LTE) is evolution of a Universal MobileTelecommunications System (UMTS) formulated by the 3rd GenerationPartnership Project (3GPP) organization. There is a packet domain in anLTE system. As shown in FIG. 1, the packet domain includes two networkelements: an evolved packet core (EPC) and an evolved NodeB (eNodeB).The EPC is responsible for a core network part. A mobility managemententity (MME) is responsible for a signaling processing part, and aserving gateway (S-GW) is responsible for a data processing part. TheeNodeB is responsible for a part of an access network that is alsoreferred to as an evolved UTRAN (E-UTRAN).

In the foregoing network architecture, when a user equipment (UE)initiates a communications service to send user-plane data, the userequipment needs to first establish a radio resource control (RRC)connection to a network side. That is, the user equipment initiates aconnection to an access network and initiates a connection to a corenetwork. Therefore, the UE switches from an idle state to a connectionstate, and further establishes a data bearer to send data. When the UEis in the connection state, a cell handover may occur if the UE moves.When the UE does not perform data transmission, an RRC connectionrelease process may be executed. Therefore, the UE returns to the idlestate. When the UE needs to perform data transmission again, a processof establishing an RRC connection to the access network and an RRCconnection to the core network, a process of establishing a data bearer,and the like are then performed. In this case, if the UE in the idlestate needs to transmit data, the UE needs to first establish the RRCconnection and the data bearer. Consequently, signaling overheads and adata transmission delay of the UE are increased. However, if the UEkeeps in the connection state, the cell handover of the UE caused bymovement of the UE increases the signaling overheads and powerconsumption of the UE.

SUMMARY

Embodiments of the present disclosure provide a signaling optimizationmethod and a device, to resolve a prior-art problem of heavy signalingoverheads and a long data transmission delay when UE accesses a networkside.

According to a first aspect, a signaling optimization method isprovided, including:

receiving, by a user equipment (UE), configuration information sent by afirst network side device, where the configuration information includesa list, and the list is a cell list or a base station list; and

entering, by the UE, an intermediate state according to theconfiguration information, where the intermediate state means that: whenthe UE stores context information of the UE, if the UE moves and a cellmovement range falls within a coverage area of a cell or a base stationincluded in the list, the UE performs cell reselection according to thelist.

With reference to the first aspect, in a first possible implementationof the first aspect, the intermediate state further means that: if thecell movement range of the UE falls beyond the coverage area of the cellor the base station included in the list, the UE sends a notificationmessage to a network side device on which a current serving cell of theUE is located, so that the UE is restored from the intermediate state toa connection state or returns to an idle state, and the network sidedevice on which the current serving cell is located is the first networkside device or a second network side device after the UE performs cellreselection.

With reference to the first aspect or the first possible implementationof the first aspect, in a second possible implementation of the firstaspect, the configuration information further includes a condition underwhich the first network side device instructs the UE to enter theintermediate state according to the configuration information, and thecondition includes entering the intermediate state immediately orentering the idle state after a preset time; and/or

the configuration information further includes a time period in whichthe first network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

With reference to the first aspect to the second possible implementationof the first aspect, in a third possible implementation of the firstaspect, the configuration information further includes a cellreselection parameter for performing cell reselection by the UE.

With reference to the first aspect to the third possible implementationof the first aspect, in a fourth possible implementation of the firstaspect, the configuration information is carried in a radio resourcecontrol (RRC) message by the first network side device, and the RRCmessage includes an RRC connection establishment message, an RRCreconfiguration message, or an RRC connection release message.

With reference to the first aspect to the fourth possible implementationof the first aspect, in a fifth possible implementation of the firstaspect, in a process in which the UE performs cell reselection, when itis determined that the UE needs to send uplink data to a network sideand/or needs to receive downlink data from the network side, the methodfurther includes:

restoring the UE to the connection state; and

sending, by the UE, the uplink data to a network side device that hasbeen restored to the connection state, and/or receiving the downlinkdata from the network side device that has been restored to theconnection state, where the network side device that has been restoredto the connection state includes the first network side device or thesecond network side device.

With reference to the fifth possible implementation of the first aspect,in a sixth possible implementation of the first aspect, the restoringthe UE to the connection state includes:

if the cell of the UE does not change, sending, by the UE, a schedulingrequest or a random access request to the first network side device, torestore the UE to the connection state.

With reference to the fifth possible implementation of the first aspect,in a seventh possible implementation of the first aspect, the restoringthe UE to the connection state includes:

sending, by the UE, an RRC resume request message to the first networkside device or the second network side device, where the RRC resumerequest message includes at least one of cell information of the firstnetwork side device, a cell radio network temporary identity (C-RNTI) ofthe UE, or indication information for requesting to restore the UE tothe connection state;

receiving, by the UE, an RRC resume confirmation message sent by thefirst network side device or the second network side device, where theRRC resume confirmation message is used to indicate that the UE isrestored to the connection state; and

sending, by the UE, an RRC connection resume completion message to thefirst network side device or the second network side device.

According to a second aspect, a signaling optimization method isprovided, including:

sending, by a first network side device, configuration information to auser equipment (UE), where the configuration information includes alist, the list is a cell list or a base station list, the configurationinformation is used to instruct the UE to enter an intermediate state,and the intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in the list,the UE performs cell reselection according to the list; and

sending, by the first network side device, the context information ofthe UE to a network side device in the list.

With reference to the second aspect, in a first possible implementationof the second aspect, the configuration information is further used toindicate that: after the UE enters the intermediate state, if the UEmoves and the cell movement range falls beyond the coverage area of thecell or the base station included in the list, the UE sends anotification message to a network side device on which a current servingcell of the UE is located, so that the UE is restored from theintermediate state to a connection state or returns to an idle state,and the network side device on which the current serving cell is locatedis the first network side device or a second network side device afterthe UE performs cell reselection.

With reference to the second aspect or the first possible implementationof the second aspect, in a second possible implementation of the secondaspect, the configuration information further includes a condition underwhich the first network side device instructs the UE to enter theintermediate state according to the configuration information, and thecondition includes entering the intermediate state immediately orentering the intermediate state after a preset time; and/or theconfiguration information further includes a time period in which thefirst network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

With reference to the second aspect to the second possibleimplementation of the second aspect, in a third possible implementationof the second aspect, the configuration information further includes acell reselection parameter for performing cell reselection by the UE.

With reference to the second aspect to the third possible implementationof the second aspect, in a fourth possible implementation of the secondaspect, the sending, by a first network side device, configurationinformation to the UE includes:

sending, by the first network side device, the configuration informationto the UE by using a radio resource control (RRC) message, where the RRCmessage includes an RRC reconfiguration message or an RRC connectionrelease message.

With reference to the second aspect to the fourth possibleimplementation of the second aspect, in a fifth possible implementationof the second aspect, the method further includes:

sending, by the first network side device, the context information ofthe UE to a core network device; and

releasing the context information of the UE when the first network sidedevice stores the context information of the UE for a preset time.

With reference to the second aspect to the fifth possible implementationof the second aspect, in a sixth possible implementation of the secondaspect, the method further includes:

receiving, by the first network side device, an RRC resume requestmessage sent by the UE, where the RRC resume request message includes atleast one of cell information of the first network side device, a cellradio network temporary identity (C-RNTI) of the UE, or indicationinformation for requesting to restore the UE to the connection state;

sending, by the first network side device, an RRC resume confirmationmessage to the UE, where the RRC resume confirmation message includes aparameter for extending, deleting, or modifying the context informationof the UE by the first network side device; and

receiving, by the first network side device, an RRC connection resumecompletion message sent by the UE.

With reference to the second aspect to the sixth possible implementationof the second aspect, in a seventh possible implementation of the secondaspect, the method further includes:

receiving, by the first network side device, an uplink schedulingrequest or a random access request sent by the UE; and

sending, by the first network side device, an uplink resource to the UE,where the uplink resource is used by the UE to send uplink data to thefirst network side device or to receive downlink data from the firstnetwork side device according to the uplink resource.

According to a third aspect, a signaling optimization method isprovided, including:

receiving, by a second network side device, indication information of auser equipment (UE) in an intermediate state that is sent by a firstnetwork side device, where the intermediate state means that: when theUE stores context information of the UE, if the UE moves and a cellmovement range falls within a coverage area of a cell or a base stationincluded in a list sent by the first network side device, the UEperforms cell reselection according to the list; and

obtaining, by the second network side device, the context information ofthe UE from the first network side device, or obtaining the contextinformation of the UE from the second network side device when thesecond network side device receives a radio resource control (RRC)resume request message sent by the UE, so as to receive uplink data fromthe UE or send downlink data to the UE.

With reference to the third aspect, in a first possible implementationof the third aspect, the method further includes:

receiving and saving, by the second network side device, contextinformation of the UE that is sent by the first network side device.

With reference to the third aspect or the first possible implementationof the third aspect, in a second possible implementation of the thirdaspect, the obtaining, by the second network side device, contextinformation of the UE from the first network side device, or obtainingthe context information of the UE from the second network side devicewhen the second network side device receives a radio resource control(RRC) resume request message sent by the UE includes:

if the second network side device does locally store the contextinformation of the UE before the second network side device receives theRRC resume request message sent by the UE, obtaining, by the secondnetwork side device, the context information of the UE from the secondnetwork side device; or

if the second network side device does not locally store the contextinformation of the UE before the second network side device receives theRRC resume request message sent by the UE, obtaining, by the secondnetwork side device, the context information of the UE from the firstnetwork side device, where

the RRC resume request message is used to be sent to the second networkside device when the UE is restored from the intermediate state to aconnection state.

With reference to the third aspect to the second possible implementationof the third aspect, in a third possible implementation of the thirdaspect, the method further includes:

when the second network side device receives a paging message sent by acore network device and determines that there is downlink data thatneeds to be sent to the UE, sending the paging message to the UE, andafter the second network side device establishes an RRC connection tothe UE, sending, to the UE, downlink data received from the core networkdevice; or

when the second network side device receives a paging message sent bythe first network side device and determines that there is downlink datathat needs to be sent to the UE, sending the paging message to the UE,and after the second network side device establishes an RRC connectionto the UE, sending, to the UE, downlink data received from the firstnetwork side device.

According to a fourth aspect, a signaling optimization method isprovided, including:

receiving, by a core network device, indication information of a userequipment (UE) in an intermediate state that is sent by the UE, wherethe intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in a listsent by a first network side device to the UE, the UE performs cellreselection according to the list; and

if the core network device needs to transmit downlink data to the UE,sending, by the core network device, a paging message to at least onenetwork side device in the list, to send the downlink data to the UE byusing a first network side device or a second network side device thatis in the at least one network side device and that is connected to theUE; or sending, by the core network device, the downlink data to thefirst network side device, to send the downlink data to the UE by usingthe first network side device; or sending, by the core network device,the downlink data to at least one network side device in the list, tosend the downlink data to the UE by using the at least one network sidedevice.

With reference to the fourth aspect, in a first possible implementationof the fourth aspect, the method further includes:

receiving and saving, by the core network device, context information ofthe UE that is sent by the first network side device.

According to a fifth aspect, a user equipment (UE) is provided,including:

a receiving unit, configured to receive configuration information sentby a first network side device, where the configuration informationincludes a list, and the list is a cell list or a base station list; and

a processing unit, configured to enter an intermediate state accordingto the configuration information, where the intermediate state meansthat: when the UE stores context information of the UE, if the UE movesand a cell movement range falls within a coverage area of a cell or abase station included in the list, the UE performs cell reselectionaccording to the list.

With reference to the fifth aspect, in a first possible implementationof the fifth aspect, the intermediate state further means that: if thecell movement range of the UE falls beyond the coverage area of the cellor the base station included in the list, the UE sends a notificationmessage to a network side device on which a current serving cell of theUE is located, so that the UE is restored from the intermediate state toa connection state or returns to an idle state, and the network sidedevice on which the current serving cell is located is the first networkside device or a second network side device after the UE performs cellreselection.

With reference to the fifth aspect to the first possible implementationof the fifth aspect, in a second possible implementation of the fifthaspect, the configuration information further includes a condition underwhich the first network side device instructs the UE to enter theintermediate state according to the configuration information, and thecondition includes entering the intermediate state immediately orentering the idle state after a preset time; and/or

the configuration information further includes a time period in whichthe first network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

With reference to the fifth aspect to the second possible implementationof the fifth aspect, in a third possible implementation of the fifthaspect, the configuration information further includes a cellreselection parameter for performing cell reselection by the UE.

With reference to the fifth aspect to the third possible implementationof the fifth aspect, in a fourth possible implementation of the fifthaspect, the configuration information is carried in a radio resourcecontrol (RRC) message by the first network side device, and the RRCmessage includes an RRC connection establishment message, an RRCreconfiguration message, or an RRC connection release message.

With reference to the fifth aspect to the fourth possible implementationof the fifth aspect, in a fifth possible implementation of the fifthaspect, in a process in which the processing unit is configured toperform cell reselection, when it is determined that the UE needs tosend uplink data to a network side and/or needs to receive downlink datafrom the network side, the processing unit is further configured torestore the UE to the connection state; and

the UE further includes: a sending unit, configured to send the uplinkdata to a network side device that has been restored to the connectionstate; and/or the receiving unit is configured to receive the downlinkdata from the network side device that has been restored to theconnection state, where the network side device that has been restoredto the connection state includes the first network side device or thesecond network side device.

With reference to the fifth possible implementation of the fifth aspect,in a sixth possible implementation of the fifth aspect, the processingunit is specifically configured to:

if the cell of the UE does not change, send a scheduling request or arandom access request to the first network side device by using thesending unit, to restore the UE to the connection state.

With reference to the fifth possible implementation of the fifth aspect,in a seventh possible implementation of the fifth aspect, when theprocessing unit is configured to restore the UE to the connection state,

the sending unit is further configured to send an RRC resume requestmessage to the first network side device or the second network sidedevice, where the RRC resume request message includes at least one ofcell information of the first network side device, a cell radio networktemporary identity (C-RNTI) of the UE, or indication information forrequesting to restore the UE to the connection state;

the receiving unit is further configured to receive an RRC resumeconfirmation message sent by the first network side device or the secondnetwork side device, where the RRC resume confirmation message is usedto indicate that the UE is restored to the connection state; and

the sending unit is further configured to send an RRC connection resumecompletion message to the first network side device or the secondnetwork side device.

According to a sixth aspect, a first network side device is provided,including:

a sending unit, configured to send configuration information to a userequipment (UE), where the configuration information includes a list, thelist is a cell list or a base station list, the configurationinformation is used to instruct the UE to enter an intermediate state,and the intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in the list,the UE performs cell reselection according to the list, where

the sending unit is further configured to send the context informationof the UE to a network side device in the list.

With reference to the sixth aspect, in a first possible implementationof the sixth aspect, the configuration information is further used toindicate that: after the UE enters the intermediate state, if the UEmoves and the cell movement range falls beyond the coverage area of thecell or the base station included in the list, the UE sends anotification message to a network side device on which a current servingcell of the UE is located, so that the UE is restored from theintermediate state to a connection state or returns to an idle state,and the network side device on which the current serving cell is locatedis the first network side device or a second network side device afterthe UE performs cell reselection.

With reference to the sixth aspect or the first possible implementationof the sixth aspect, in a second possible implementation of the sixthaspect, the configuration information further includes a condition underwhich the first network side device instructs the UE to enter theintermediate state according to the configuration information, and thecondition includes entering the intermediate state immediately orentering the intermediate state after a preset time; and/or

the configuration information further includes a time period in whichthe first network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

With reference to the sixth aspect to the second possible implementationof the sixth aspect, in a third possible implementation of the sixthaspect, the configuration information further includes a cellreselection parameter for performing cell reselection by the UE.

With reference to the sixth aspect to the third possible implementationof the sixth aspect, in a fourth possible implementation of the sixthaspect, the sending unit is specifically configured to:

send the configuration information to the UE by using a radio resourcecontrol (RRC) message, where the RRC message includes an RRCreconfiguration message or an RRC connection release message.

With reference to the sixth aspect to the fourth possible implementationof the sixth aspect, in a fifth possible implementation of the sixthaspect, the sending unit is further configured to send the contextinformation of the UE to a core network device; and

the first network side device further includes: a processing unit,configured to release the context information of the UE when the firstnetwork side device stores the context information of the UE for apreset time.

With reference to the sixth aspect to the fifth possible implementationof the sixth aspect, in a sixth possible implementation of the sixthaspect, the first network side device further includes:

a receiving unit, configured to receive an RRC resume request messagesent by the UE, where the RRC resume request message includes at leastone of cell information of the first network side device, a cell radionetwork temporary identity (C-RNTI) of the UE, or indication informationfor requesting to restore the UE to the connection state, where

the sending unit is further configured to send an RRC resumeconfirmation message to the UE, where the RRC resume confirmationmessage includes a parameter for extending, deleting, or modifying thecontext information of the UE by the first network side device; and

the receiving unit is further configured to receive an RRC connectionresume completion message sent by the UE.

With reference to the sixth aspect to the sixth possible implementationof the sixth aspect, in a seventh possible implementation of the sixthaspect, the receiving unit is further configured to receive an uplinkscheduling request or a random access request sent by the UE; and

the sending unit is further configured to send an uplink resource to theUE, where the uplink resource is used by the UE to send uplink data tothe first network side device or to receive downlink data from the firstnetwork side device according to the uplink resource.

According to a seventh aspect, a second network side device is provided,including:

a receiving unit, configured to receive indication information of a userequipment (UE) in an intermediate state that is sent by a first networkside device, where the intermediate state means that: when the UE storescontext information of the UE, if the UE moves and a cell movement rangefalls within a coverage area of a cell or a base station included in alist sent by the first network side device, the UE performs cellreselection according to the list; and

an obtaining unit, configured to obtain the context information of theUE from the first network side device, or obtain the context informationof the UE from the second network side device when a radio resourcecontrol (RRC) resume request message sent by the UE is received, so asto receive uplink data from the UE or send downlink data to the UE.

With reference to the seventh aspect, in a first possible implementationof the seventh aspect, the receiving unit is further configured to:

receive and save context information of the UE that is sent by the firstnetwork side device.

With reference to the seventh aspect or the first possibleimplementation of the seventh aspect, in a second possibleimplementation of the seventh aspect, the obtaining unit is specificallyconfigured to:

if the second network side device does locally store the contextinformation of the UE before the second network side device receives theRRC resume request message sent by the UE, obtain the contextinformation of the UE from the second network side device; or

if the second network side device does not locally store the contextinformation of the UE before the second network side device receives theRRC resume request message sent by the UE, obtain the contextinformation of the UE from the first network side device, where

the RRC resume request message is used to be sent to the second networkside device when the UE is restored from the intermediate state to aconnection state.

With reference to the seventh aspect to the second possibleimplementation of the seventh aspect, in a third possible implementationof the seventh aspect, the second network side device further includes:a sending unit, configured to: when the second network side devicereceives a paging message sent by a core network device and determinesthat there is the downlink data that needs to be sent to the UE, sendthe paging message to the UE, and after the second network side deviceestablishes an RRC connection to the UE, send, to the UE, the downlinkdata received from the core network device; or

the sending unit, configured to: when a paging message sent by the firstnetwork side device is received and it is determined that there is thedownlink data that needs to be sent to the UE, send the paging messageto the UE, and after the second network side device establishes an RRCconnection to the UE, send, to the UE, the downlink data received fromthe first network side device.

According to an eighth aspect, a core network device is provided,including:

a receiving unit, configured to receive indication information of a userequipment (UE) in an intermediate state that is sent by the UE, wherethe intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in a listsent by a first network side device to the UE, the UE performs cellreselection according to the list; and

a sending unit, configured to: if the core network device needs totransmit downlink data to the UE, send a paging message to at least onenetwork side device in the list, to send the downlink data to the UE byusing a first network side device or a second network side device thatis in the at least one network side device and that is connected to theUE; or send the downlink data to the first network side device, to sendthe downlink data to the UE by using the first network side device; orsend the downlink data to at least one network side device in the list,to send the downlink data to the UE by using the at least one networkside device.

With reference to the eighth aspect, in a first possible implementationof the eighth aspect, the receiving unit is further configured toreceive and save context information of the UE that is sent by the firstnetwork side device.

According to a ninth aspect, user equipment is provided, including:

a receiver, configured to receive configuration information sent by afirst network side device, where the configuration information includesa list, and the list is a cell list or a base station list; and

a processor, configured to enter an intermediate state according to theconfiguration information, where the intermediate state means that: whenthe UE stores context information of the UE, if the UE moves and a cellmovement range falls within a coverage area of a cell or a base stationincluded in the list, the UE performs cell reselection according to thelist.

With reference to the ninth aspect, in a first possible implementationof the ninth aspect, the intermediate state further means that: if thecell movement range of the UE falls beyond the coverage area of the cellor the base station included in the list, the UE sends a notificationmessage to a network side device on which a current serving cell of theUE is located, so that the UE is restored from the intermediate state toa connection state or returns to an idle state, and the network sidedevice on which the current serving cell is located is the first networkside device or a second network side device after the UE performs cellreselection.

With reference to the ninth aspect or the first possible implementationof the ninth aspect, in a second possible implementation of the ninthaspect, the configuration information further includes a condition underwhich the first network side device instructs the UE to enter theintermediate state according to the configuration information, and thecondition includes entering the intermediate state immediately orentering the idle state after a preset time; and/or

the configuration information further includes a time period in whichthe first network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

With reference to the ninth aspect to the second possible implementationof the ninth aspect, in a third possible implementation of the ninthaspect, the configuration information further includes a cellreselection parameter for performing cell reselection by the UE.

With reference to the ninth aspect to the third possible implementationof the ninth aspect, in a fourth possible implementation of the ninthaspect, the configuration information is carried in a radio resourcecontrol (RRC) message by the first network side device, and the RRCmessage includes an RRC connection establishment message, an RRCreconfiguration message, or an RRC connection release message.

With reference to the ninth aspect to the fourth possible implementationof the ninth aspect, in a fifth possible implementation of the ninthaspect, in a process in which the processor is configured to performcell reselection, when it is determined that the UE needs to send uplinkdata to a network side and/or needs to receive downlink data from thenetwork side, the processor is further configured to restore the UE tothe connection state; and the UE further includes: a transmitter,configured to send the uplink data to a network side device that hasbeen restored to the connection state; and/or the receiver is configuredto receive the downlink data from the network side device that has beenrestored to the connection state, where the network side device that hasbeen restored to the connection state includes the first network sidedevice or the second network side device.

With reference to the fifth possible implementation of the ninth aspect,in a sixth possible implementation of the ninth aspect, the transmitteris specifically configured to:

if the cell of the UE does not change, send a scheduling request or arandom access request to the first network side device, to restore theUE to the connection state.

With reference to the fifth possible implementation of the ninth aspect,in a seventh possible implementation of the ninth aspect, thetransmitter is further configured to send an RRC resume request messageto the first network side device or the second network side device,where the RRC resume request message includes at least one of cellinformation of the first network side device, a cell radio networktemporary identity (C-RNTI) of the UE, or indication information forrequesting to restore the UE to the connection state;

the receiver is further configured to receive an RRC resume confirmationmessage sent by the first network side device or the second network sidedevice, where the RRC resume confirmation message is used to indicatethat the UE is restored to the connection state; and

the transmitter is further configured to send an RRC connection resumecompletion message to the first network side device or the secondnetwork side device.

According to a tenth aspect, a first network side device is provided,including:

a transmitter, configured to send configuration information to a userequipment (UE), where the configuration information includes a list, thelist is a cell list or a base station list, the configurationinformation is used to instruct the UE to enter an intermediate state,and the intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in the list,the UE performs cell reselection according to the list, where

the transmitter is further configured to send the context information ofthe UE to a network side device in the list.

With reference to the tenth aspect, in a first possible implementationof the tenth aspect, the configuration information is further used toindicate that: after the UE enters the intermediate state, if the UEmoves and the cell movement range falls beyond the coverage area of thecell or the base station included in the list, the UE sends anotification message to a network side device on which a current servingcell of the UE is located, so that the UE is restored from theintermediate state to a connection state or returns to an idle state,and the network side device on which the current serving cell is locatedis the first network side device or a second network side device afterthe UE performs cell reselection.

With reference to the tenth aspect or the first possible implementationof the tenth aspect, in a second possible implementation of the tenthaspect, the configuration information further includes a condition underwhich the first network side device instructs the UE to enter theintermediate state according to the configuration information, and thecondition includes entering the intermediate state immediately orentering the intermediate state after a preset time; and/or

the configuration information further includes a time period in whichthe first network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

With reference to the tenth aspect to the second possible implementationof the tenth aspect, in a third possible implementation of the tenthaspect, the configuration information further includes a cellreselection parameter for performing cell reselection by the UE.

With reference to the tenth aspect to the second possible implementationof the tenth aspect, in a third possible implementation of the tenthaspect, the transmitter is specifically configured to:

send the configuration information to the UE by using a radio resourcecontrol (RRC) message, where the RRC message includes an RRCreconfiguration message or an RRC connection release message.

With reference to the tenth aspect to the third possible implementationof the tenth aspect, in a fourth possible implementation of the tenthaspect, the transmitter is further configured to send the contextinformation of the UE to a core network device; and

the first network side device further includes: a processor, configuredto release the context information of the UE when the first network sidedevice stores the context information of the UE for a preset time.

With reference to the tenth aspect to the fourth possible implementationof the tenth aspect, in a fifth possible implementation of the tenthaspect, the first network side device further includes:

a receiver, configured to receive an RRC resume request message sent bythe UE, where the RRC resume request message includes at least one ofcell information of the first network side device, a cell radio networktemporary identity (C-RNTI) of the UE, or indication information forrequesting to restore the UE to the connection state, where

the transmitter is further configured to send an RRC resume confirmationmessage to the UE, where the RRC resume confirmation message includes aparameter for extending, deleting, or modifying the context informationof the UE by the first network side device; and

the receiver is further configured to receive an RRC connection resumecompletion message sent by the UE.

With reference to the tenth aspect to the fifth possible implementationof the tenth aspect, in a sixth possible implementation of the tenthaspect, the receiver is further configured to receive an uplinkscheduling request or a random access request sent by the UE; and

the transmitter is further configured to send an uplink resource to theUE, where the uplink resource is used by the UE to send uplink data tothe first network side device or to receive downlink data from the firstnetwork side device according to the uplink resource.

According to an eleventh aspect, a second network side device isprovided, including:

a receiver, configured to receive indication information of a userequipment (UE) in an intermediate state that is sent by a first networkside device, where the intermediate state means that: when the UE storescontext information of the UE, if the UE moves and a cell movement rangefalls within a coverage area of a cell or a base station included in alist sent by the first network side device, the UE performs cellreselection according to the list; and

a processor, configured to obtain the context information of the UE fromthe first network side device, or obtain the context information of theUE from the second network side device when the receiver receives aradio resource control (RRC) resume request message sent by the UE, soas to receive uplink data from the UE or send downlink data to the UE.

With reference to the eleventh aspect, in a first possibleimplementation of the eleventh aspect, the receiver is furtherconfigured to receive and save context information of the UE that issent by the first network side device.

With reference to the eleventh aspect or the first possibleimplementation of the eleventh aspect, in a second possibleimplementation of the eleventh aspect, the processor is specificallyconfigured to: if a memory does not store the context information of theUE when the receiver receives the radio resource control (RRC) resumerequest message sent by the UE, obtain the context information of the UEfrom the memory; or

if a memory does not store the context information of the UE before thereceiver receives the RRC resume request message sent by the UE, obtainthe context information of the UE from the first network side device,where

the RRC resume request message is used to be sent to the second networkside device when the UE is restored from the intermediate state to aconnection state.

With reference to the eleventh aspect to the second possibleimplementation of the eleventh aspect, in a third possibleimplementation of the eleventh aspect, the second network side devicefurther includes: a transmitter, configured to: when the second networkside device receives a paging message sent by a core network device anddetermines that there is the downlink data that needs to be sent to theUE, send the paging message to the UE, and after the second network sidedevice establishes an RRC connection to the UE, send, to the UE, thedownlink data received from the core network device; or

the transmitter, configured to: when a paging message sent by the firstnetwork side device is received and it is determined that there is thedownlink data that needs to be sent to the UE, send the paging messageto the UE, and after the second network side device establishes an RRCconnection to the UE, send, to the UE, the downlink data received fromthe first network side device.

According to a twelfth aspect, a core network device is provided,including:

a receiver, configured to receive indication information of a userequipment (UE) in an intermediate state that is sent by the UE, wherethe intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in a listsent by a first network side device to the UE, the UE performs cellreselection according to the list; and

a transmitter, configured to: if the core network device needs totransmit downlink data to the UE, send a paging message to at least onenetwork side device in the list, to send the downlink data to the UE byusing a first network side device or a second network side device thatis in the at least one network side device and that is connected to theUE; or send the downlink data to the first network side device, to sendthe downlink data to the UE by using the first network side device; orsend the downlink data to at least one network side device in the list,to send the downlink data to the UE by using the at least one networkside device.

With reference to the twelfth aspect, in a first possible implementationof the twelfth aspect, the receiver is further configured to receive andsave context information of the UE that is sent by the first networkside device.

The embodiments of the present disclosure provide a signalingoptimization method and a device. UE receives configuration informationsent by a first network side device. The configuration informationincludes a list. The list is a cell list or a base station list. The UEenters an intermediate state according to the configuration information.The intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in the list,the UE performs cell reselection according to the list. In this way, incomparison with the prior art, in the embodiments of the presentdisclosure, UE does not perform a cell handover, but cell reselection isperformed, so as to reduce signaling overheads of the UE and a networkside. In the prior art, UE is restored from an idle state to aconnection state, and context of the UE is re-established. In comparisonwith the prior art, in the embodiments of the present disclosure, evenif the UE needs to be restored from an intermediate state to aconnection state, because UE stores context information of the UE, theUE does not need to re-establish an RRC connection to a network side andestablish the context information. Therefore, a problem of heavysignaling overheads and a long data transmission delay when UE accessesa network side in the prior art can be resolved.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentdisclosure more clearly, the following briefly describes theaccompanying drawings required for describing the embodiments or theprior art. Apparently, the accompanying drawings in the followingdescription show merely some embodiments of the present disclosure, andpersons of ordinary skill in the art may still derive other drawingsfrom these accompanying drawings without creative efforts.

FIG. 1 is a schematic diagram of an LTE system according to anembodiment of the present disclosure;

FIG. 2 is a schematic flowchart of a signaling optimization methodaccording to an embodiment of the present disclosure;

FIG. 3 is a schematic flowchart of a signaling optimization methodaccording to an embodiment of the present disclosure;

FIG. 4 is a schematic flowchart of a signaling optimization methodaccording to an embodiment of the present disclosure;

FIG. 5 is a schematic flowchart of a signaling optimization methodaccording to an embodiment of the present disclosure;

FIG. 6 is a schematic flowchart of a signaling optimization methodaccording to an embodiment of the present disclosure;

FIG. 7a -1 and FIG. 7a -2 are a schematic flowchart of a signalingoptimization method according to an embodiment of the presentdisclosure;

FIG. 7b is a schematic flowchart of a signaling optimization methodaccording to an embodiment of the present disclosure;

FIG. 8 is a schematic structural diagram of user equipment according toan embodiment of the present disclosure;

FIG. 9 is a schematic structural diagram of a first network side deviceaccording to an embodiment of the present disclosure;

FIG. 10 is a schematic structural diagram of user equipment according toan embodiment of the present disclosure;

FIG. 11 is a schematic structural diagram of a first network side deviceaccording to an embodiment of the present disclosure;

FIG. 12 is a schematic structural diagram of a second network sidedevice according to an embodiment of the present disclosure;

FIG. 13 is a schematic structural diagram of a core network deviceaccording to an embodiment of the present disclosure;

FIG. 14 is a schematic structural diagram of a second network sidedevice according to an embodiment of the present disclosure; and

FIG. 15 is a schematic structural diagram of a core network deviceaccording to an embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

The following clearly describes the technical solutions in theembodiments of the present disclosure with reference to the accompanyingdrawings in the embodiments of the present disclosure. Apparently, thedescribed embodiments are merely some but not all of the embodiments ofthe present disclosure. All other embodiments obtained by persons ofordinary skill in the art based on the embodiments of the presentdisclosure without creative efforts shall fall within the protectionscope of the present disclosure.

In a wireless communications system, a cell handover in the embodimentsof the present disclosure is channel switching that needs to beperformed to ensure that communication of a mobile user is notinterrupted when a mobile station moves from a cell (a base station or acoverage area of a base station) to another cell.

Cell reselection in the embodiments of the present disclosure means thatthe UE in an idle state needs to monitor a signal of a current cell anda neighboring cell, such as a signal level, signal strength, and signalquality, and select, as a current serving cell, a cell with relativelyhigh strength or quality or a cell whose signal strength or signalquality reaches a threshold.

An embodiment of the present disclosure provides a signalingoptimization method. As shown in FIG. 2, the method includes thefollowing steps.

201. A user equipment (UE) receives configuration information sent by afirst network side device, where the configuration information includesa list, and the list is a cell list or a base station list.

Specifically, the cell list includes a cell identifier of at least onecell, and the base station list includes a base station identifier of atleast one base station.

It can be understood that the foregoing cell list or the base stationlist may also be replaced with a tracking area or a tracking area list.This is not limited in the present disclosure.

Optionally, the configuration information may further includeinformation that instructs the UE to enter an intermediate state.

202. The UE enters an intermediate state according to the configurationinformation, where the intermediate state means that: when the UE storescontext information of the UE, if the UE moves and a cell movement rangefalls within a coverage area of a cell or a base station included in thelist, the UE performs cell reselection according to the list.

The context information of the UE includes at least information that theUE is in the intermediate state. If the cell movement range of the UEfalls beyond the coverage area of the cell or the base station includedin the list, the UE sends a notification message to a network sidedevice on which a current serving cell of the UE is located, so that theUE is restored from the intermediate state to a connection state orreturns to an idle state. The network side device on which the currentserving cell is located is the first network side device or a secondnetwork side device after the UE performs cell reselection.

The network side device may be an evolved NodeB eNB, a base station, aradio network controller, or the like. When the UE establishes an RRCconnection to the base station to be in the connection state, asignaling radio bearer (SRB) 1 is established between the UE and thenetwork side device. The network side device stores the contextinformation of the UE, and further includes information about whetherthe UE is in the intermediate state. Then, in step 201, the UE receivesthe configuration information sent by the first network side device. Theconfiguration information may be the cell list or the base station list.The cell list may be a list of neighboring cells of a cell in which theUE is currently located, and may also include multiple cells at adistance from the cell in which the UE is currently located. Forexample, the cell list includes cell identifiers of a neighboring celland a separated cell. The base station list is similar to the cell list.The base station list may include an identifier of a base station thatis neighboring to a base station in which the UE is currently locatedand an identifier of a base station at a distance from the base stationin which the UE is currently located. The cell list may also be thetracking area or the tracking area list. The tracking area or thetracking area list is corresponding to or includes the cell list. Thisis not limited in the present disclosure.

The list is used to indicate that: if the UE moves and moves within arange of the list, the UE may automatically perform cell reselection,and does not need to notify the network side device; or if the UE movesoutside a range of the list, the UE needs to notify the network sidedevice. In the prior art, if the UE is in the connection state and movesfrom a cell to another cell, a cell handover needs to be performed; andif the UE is in the idle state and moves from a cell to another cell,cell reselection needs to be performed. In comparison with the priorart, in the embodiments of the present disclosure, when the UE in theconnection state receives configuration information sent by the networkside device, cell reselection is performed if the cell changes, that is,the UE is intermediate between the connection state and the idle state.Therefore, in step 201 and 202, the UE may enter the intermediate stateaccording to the configuration information. The intermediate state meansthat: when the UE stores the context information, if the UE moves and acell movement range falls within the list, the UE performs cellreselection; or if a cell movement range of the UE falls beyond thelist, the UE sends a notification message to the network side device, sothat the UE is restored from the intermediate state to the connectionstate or returns to the idle state.

In the prior art, if a cell changes when the UE is in a connectionstate, a cell handover needs to be performed. A process of the cellhandover includes interaction between the UE and a network side devicesuch as an eNB. The UE reports a measurement report to the network sidedevice after a requirement is met. Then, the network side deviceperforms handover determining in combination with an algorithm policy.Finally, the UE performs a cell handover. However, in the embodiments ofthe present disclosure, if a cell changes when UE is in a connectionstate, a cell handover is not performed, but a cell reselection processis performed. In this way, the UE does not need to communicate with anetwork side, but the UE automatically performs cell reselectionaccording to a cell reselection criterion, so as to reduce signalingoverheads when the UE moves, and save power for the UE. In the priorart, when UE is in an idle state when no data needs to be sent, the UEreleases context information of the UE, and needs to re-establish an RRCconnection to a network side when there is data that needs to be sent.However, in the embodiments of the present disclosure, UE stores contextinformation of the UE, and when the UE needs to be restored from anintermediate state to a connection state, to perform data transmission,the UE does not need to execute a process of re-establishing the contextinformation with a network side device, so as to reduce signalingoverheads, shorten a data transmission delay, and save power for the UE.

Corresponding to the foregoing embodiment, an embodiment of the presentdisclosure provides a signaling optimization method. As shown in FIG. 3,the method includes the following steps.

301. A first network side device sends configuration information to theUE, where the configuration information includes a list, the list is acell list or a base station list, the configuration information is usedto instruct the UE to enter an intermediate state, and the intermediatestate means that: when the UE stores context information of the UE, ifthe UE moves and a cell movement range falls within a coverage area of acell or a base station included in the list, the UE performs cellreselection according to the list.

The context information of the UE includes at least information that theUE is in the intermediate state.

302. The first network side device sends the context information to anetwork side device in the list.

The first network side device still stores the context information ofthe UE. Further, the first network side device may send the contextinformation of the UE to the network side device in the list. Therefore,when the UE performs cell reselection to a cell of another network sidedevice in the list, the UE does not need to establish the contextinformation of the UE with the another network side device.

This step is optional.

This embodiment of the present disclosure provides a signalingoptimization method. The UE receives configuration information sent by afirst network side device. The configuration information includes alist. The list is a cell list or a base station list. The UE enters anintermediate state according to the configuration information. Theintermediate state means that: when the UE stores context information ofthe UE, if the UE moves and a cell movement range falls within acoverage area of a cell or a base station included in the list, the UEperforms cell reselection according to the list; or if the cell movementrange of the UE falls beyond the list, the UE sends a notificationmessage to the first network side device, so that the UE is restoredfrom the intermediate state to a connection state or an idle state. Incomparison with the prior art, in the embodiments of the presentdisclosure, UE in a connection state does not perform cell handover, butperforms cell reselection. In the prior art, UE re-establishes contextof the UE when the UE is restored from an idle state to a connectionstate. In comparison with the prior art, in the embodiments of thepresent disclosure, because UE stores context information of the UE, ina process in which the UE is restored from an intermediate state to aconnection state, an RRC connection to a network side does not need tobe re-established, and the context information does not need to beestablished. Therefore, a problem of heavy signaling overheads and along data transmission delay when UE accesses a network side in theprior art can be resolved.

The following further describes the embodiments of the presentdisclosure, and provides a signaling optimization method. As shown inFIG. 4, the method includes the following steps.

401. The UE establishes an RRC connection to a first network sidedevice, and enters an RRC connection state.

Specifically, the UE may send random access code to the first networkside device, receive a random access response sent by the first networkside device, send an RRC connection establishment request message to thefirst network side device according to an uplink grant in the randomaccess response, and then receive an RRC connection establishmentmessage sent by the first network side device. The UE adopts aconfiguration parameter in the RRC connection establishment message, andsends an RRC connection establishment completion message to the firstnetwork side device. The UE enters the RRC connection state. In thisway, the UE and the first network side device establish contextinformation of the UE, including a signaling radio bearer SRB 1.

The context information of the UE may include: an identifier of the UE,for example, a cell radio network temporary identity (C-RNTI) allocatedby the first network side device to the UE; radio bearer configurationinformation of the UE, for example, an SRB and/or a data radio bearer(DRB); a Media Access Control (MAC) layer configuration parameter of theUE, for example, buffer status report (BSR) parameter configuration,power headroom report (PHR) parameter configuration, and a discontinuousreception (DRX); physical layer parameter configuration of the UE, forexample, parameter configuration related to each physical layer channel;and a security-related parameter of the UE, for example, a security key,and a security algorithm.

This step is optional.

402. The first network side device sends configuration information tothe UE, where the configuration information includes a list, and thelist is a cell list or a base station list.

Optionally, the configuration information may further includeinformation that instructs the UE to enter an intermediate state.

The cell list or the base station list is used to indicate that: if theUE moves and a movement range falls within the list, the UE mayautomatically perform cell reselection, and does not need to notify anetwork side device; or further used to indicate that if the UE movesand a movement range falls beyond the list, the UE needs to notify anetwork side device.

Optionally, the configuration information may be carried in a systembroadcast message by the first network side device, or may be carried ina dedicated message. The dedicated message may be carried in a radioresource control (RRC) message. The RRC message may be an RRC connectionestablishment message, an RRC reconfiguration message, or an RRCconnection release message, or another new RRC message. This is notlimited in the present disclosure. Optionally, the configurationinformation may be carried in another message such as a MAC layermessage, or may be carried in a physical layer (PHY) message. Theconfiguration information may be carried in a message, or may beseparately carried in multiple messages, for example, a combination of asystem broadcast message and a dedicated message. This is not limited inthe present disclosure.

403. The UE enters an intermediate state according to the configurationinformation, where the intermediate state means that: when the UE storescontext information of the UE, if the UE moves and a cell movement rangefalls within the list, the UE performs cell reselection according to thelist.

Alternatively, if a cell movement range of the UE falls beyond the list,the UE sends a notification message to the first network side device, sothat the UE is restored from an intermediate state to the connectionstate.

Specifically, that the UE stores the context information means that theUE stores one or more of radio bearer parameter configurationinformation, MAC layer parameter configuration information, physicalresource configuration information, a maintained timer, or statusvariable information.

The configuration information may also include a condition under whichthe first network side device instructs the UE to enter the intermediatestate. The condition may be using the configuration informationimmediately, that is, the UE enters the intermediate state immediately;or may be using the configuration information after a preset time, thatis, the UE enters the intermediate state after the preset time; or maybe that the UE uses the configuration information when there is no datatransmission in a specific time, to enter the intermediate state; or thelike.

Optionally, the configuration information may further include a timeperiod in which the first network side device instructs the UE to enterthe intermediate state according to the configuration information,and/or an operation instruction performed after the UE enters theintermediate state during the time period according to the configurationinformation. The operation instruction may be used to instruct the UE toenter the idle state and/or instruct the UE to notify the first networkside device of current location information of the UE.

404. After the UE enters the intermediate state, if the UE moves and acell movement range falls within the list, the UE performs cellreselection.

Specifically, the UE may perform cell reselection based on a cellreselection criterion, for example, the UE camps on a current servingcell for more than 1 s, or a cell selection evaluation measurement valueof a current serving cell is less than a reselection threshold of anintra-frequency cell, an inter-frequency cell, an inter-system cell, orthe like.

A cell reselection parameter for performing cell reselection by the UEmay be obtained by receiving, by the UE, a system broadcast message of aserving cell in which the UE is located. For example, if the currentserving cell of the UE is a cell 1, the UE may read a system broadcastmessage of the cell 1 to obtain a cell reselection parameter forreselecting another cell instead of the cell 1; and when reselecting acell 2 instead of the cell 1, the UE reads a system broadcast message ofthe cell 2 to obtain a cell reselection parameter for reselectinganother cell instead of the cell 2. Optionally, the cell reselectionparameter may be carried in the configuration information sent by thefirst network side device. For example, a set of cell reselectionparameters is notified, or each cell in the list is notified of a set ofcell reselection parameters. Alternatively, the cell reselectionparameter may be obtained by using a system broadcast message of a cellthat receives the configuration information.

405. The first network side device sends the context information of theUE to a network side device in the list.

The context information of the UE may include indication information ofthe UE in the intermediate state. Alternatively, the first network sidedevice separately sends the indication information of the UE in theintermediate state and the context information of the UE to the networkside device in the list.

After the first network side device sends the configuration informationto the UE, the first network side device may send the contextinformation of the UE to the network side device in the list, so thatthe network side device in the list also stores the context informationof the UE. In this way, when reselecting another network side device inthe list, the UE may not establish the context information of the UEwith the another network side device.

Optionally, the first network side device may send the contextinformation of the UE to a core network device, for example, to amobility management entity (MME), so that the core network device storesthe context information of the UE.

For example, the first network side device may send the contextinformation of the UE to the network side device in the list by using anX2 interface, or send the context information of the UE to the networkside device in the list by using the core network device through an S1interface. This is not limited in the present disclosure.

Optionally, the first network side device and/or the network side devicein the list may release the context information of the UE when contextinformation of the UE that is stored the first network side deviceand/or the network side device in the list reaches a configured timelength, that is, the context information of the UE is not stored.

It can be understood that the first network side device and the networkside device in the list may be a same network side device. In this case,this step is implemented inside a network side.

This step is optional.

In the prior art, if a cell changes, the UE in a connection stateperforms a cell handover. In this way, in comparison with the prior art,in the embodiments of the present disclosure, UE may be in anintermediate state when receiving configuration information; if a cellchanges, the UE needs to perform cell reselection, so as to avoidsignaling exchange with a network side, and reduce signaling overheads;context information of the UE is stored, so that when being restored toa connection state, the UE does not need to establish the contextinformation of the UE with the network side, so as to further reducesignaling overheads.

Further, if the UE is in the intermediate state, the UE needs to berestored from the intermediate state to the connection state when the UEneeds to transmit data, perform a tracking area update (TAU), or thelike.

For example, the UE needs to be restored to the connection state whenthe UE in the intermediate state determines that there is uplink datathat needs to be sent to a second network side device. Specifically, forexample, when there is data reaching a packet data convergence protocol(PDCP) layer, an RRC layer may be notified by using the PDCP layer; orwhen there is data reaching an internet protocol (IP) layer, an RRClayer may be notified by the IP layer, so that the RRC layer isconnected to the network side, to restore the UE to the connectionstate.

Alternatively, the UE in the intermediate state needs to be restoredfrom the intermediate state to the connection state when the UE in theintermediate state determines that there is downlink data that needs tobe received. For example, the UE is restored to the connection statewhen receiving a paging message sent by a network side device.

Alternatively, the UE in the intermediate state needs to be restored tothe connection state when the UE in the intermediate state needs toperform tracking area update (TAU). For example, a TAU program needs tobe executed when the TAU is periodically performed, or when a trackingarea identity (TAI) is not in a TA list obtained when the UE performsregistration.

Alternatively, the UE is restored to the connection state when being inthe intermediate state for a preset time length.

Alternatively, the UE is restored to the connection state when a cell inwhich the UE is currently located is not in a list sent by the networkside device; or the like.

Based on the foregoing steps 401 to 405, as shown in FIG. 5, the methodfurther includes the following steps.

501. If it is determined that the UE needs to be restored to theconnection state, the UE in the intermediate state sends an RRC resumerequest message to a second network side device corresponding to acurrent serving cell.

The RRC resume request message includes first cell information.Specifically, if the cell of the UE does not change, the second networkside device is the same as the first network side device, and the firstcell information included in the RRC resume request message may be cellinformation of the second network side device or the first network sidedevice. Alternatively, if the cell of the UE changes and the UE moves toa cell of the second network side device in the list, the first networkside device is different from the second network side device, and thecell information included in the RRC resume request message may be cellinformation of the first network side device, and specifically, may be aserving cell that sends the configuration information to the UE. It canbe understood that when the cell of the UE does not change, the RRCresume request message may not include the first cell information.

In addition, the RRC resume request message may further include a C-RNTIcorresponding to the UE. The C-RNTI may be sent by the first networkside device that sends the configuration information to the UE; or maybe allocated to the UE by a second network side device that receives theconfiguration information from the first network side device, and besent by using the first network side device. It can be understood thatwhen the cell of the UE does not change, the RRC resume request messagemay not include the first cell information and/or the C-RNTIcorresponding to the UE.

The RRC resume request message may further include indicationinformation for requesting to restore the UE to the connection state.For example, the indication information may perform indication by usinga message type of the RRC resume request message, and this typeindicates that the UE requests to be restored to the connection state.Alternatively, the indication information may perform indication byusing a cause value carried in the RRC resume request message, and thecause value indicates that the UE needs to be restored to the connectionstate. Alternatively, the indication information may be carried by usinga logical channel identifier (LCID) in a MAC header of the RRC resumerequest message. This is not limited in the present disclosure.

Optionally, encryption and/or integrity protection may be performed onthe RRC resume request message by using a security parameter. Thesecurity parameter is configured for the UE and sent to the UE by thefirst network side device; or the security parameter is configured bythe second network side device for the UE and sent to the UE by usingthe first network side device. Further, optionally, the RRC resumerequest message may be sent by using the SRB 1 established between thefirst network side device and the UE.

502. After receiving the RRC resume request message, the second networkside device obtains the context information of the UE.

Specifically, the second network side device may first determine whetherthe second network side device stores the context information of the UE.If the second network side device stores the context information of theUE, the second network side device may directly obtain the contextinformation from the second network side device. In this case, thesecond network side device and the first network side device may be asame device, that is, the cell of the UE does not change; or the secondnetwork side device may be any network side device in the list. If thesecond network side device does not store the context information of theUE, the second network side device may request the context informationfrom the first network side device. For example, it is possible that theUE needs to be restored to the connection state before the first networkside device notifies the second network side device of the contextinformation of the UE. For example, the second network side device maysend a context obtaining request message to the first network sidedevice by using the X2 interface to obtain the context information ofthe UE. The message may carry the C-RNTI of the UE. Optionally, thecontext information of the UE may be obtained by requesting the corenetwork device by the second network side device by using the S1interface.

Optionally, the first network side device may release the contextinformation of the UE after sending context information of the UE to thesecond network side device.

It can be understood that another behavior of the second network sidedevice includes: The second network side device may reject the RRCconnection resume request message of the UE, and specifically, may sendan RRC connection resume rejection message to the UE.

Further, optionally, the second network side device instructs the firstnetwork side device to release the context information of the UE.

Further, optionally, the UE returns to the idle state after receivingthe RRC connection resume rejection message.

503. After obtaining the context information of the UE, the secondnetwork side device sends an RRC connection resume confirmation messageto the UE.

Optionally, the RRC connection resume confirmation message may include achanged parameter in the context information of the UE, for example, anewly-added, deleted, or modified parameter. An unchanged parameter maybe not carried in the RRC connection resume confirmation message.Alternatively, the RRC connection resume confirmation message mayinclude all parameters of the context information of the UE, includingboth the changed parameter and the unchanged parameter.

The RRC connection resume confirmation message may be transmitted byusing the SRB 1, for example, may use a parameter of the SRB 1established between the first network side device and the UE.

504. After receiving the RRC connection resume confirmation message sentby the second network side device, the UE sends an RRC connection resumecompletion message to the second network side device.

This step is optional.

Further, optionally, the second network side device may send a pathswitching request message to the core network device. The path switchingrequest message is used to request the core network device to switch adata channel from a path between the first network side device and thecore network device to a path between the second network side device andthe core network device, so that a core network learns that a networkside device of the serving cell in which the UE is currently located isthe second network side device. Further, the core network device sends apath switching confirmation message to the second network side device.In this way, data transmission can be performed between the UE, thesecond network side device, and the core network device.

Further, optionally, after path switching, the second network sidedevice instructs the first network side device to release the contextinformation of the UE; or the core network device instructs the firstnetwork side device to release the context information of the UE.

Further, a network side device in a cell list of the first network sidedevice releases the context information of the UE.

In the prior art, when UE is in an idle state, context information ofthe UE is released. If the UE needs to be restored to a connectionstate, the context information of the UE needs to be re-established. TheUE and a network side need to perform signaling transmission formultiple times. This brings a long data transmission delay. Incomparison with the process in which the UE is restored from the idlestate to the connection state in the prior art, in the embodiments ofthe present disclosure, if UE is restored from an intermediate state toa connection state, the UE sends an RRC resume request message to anetwork side device, and receives an RRC connection resume confirmationmessage sent by the network side device; then, the UE sends an RRCconnection resume completion message to the network side device, so thatthe UE can be restored from the intermediate state to the connectionstate, and further send data. In this way, signaling overheads in an RRCconnection resume process are reduced, and a data transmission delay isshortened.

Still further, when the UE is in the intermediate state, a signaling anddata transmission processing method may be as follows.

As shown in FIG. 6, when there is uplink data that needs to be sent tothe network side device or the TAU needs to be performed, the method mayfurther include the following steps.

601. The UE determines whether a cell changes; then, go to step 602 orstep 603.

For example, when the cell of the UE does not change, the second networkside device is the same as the first network side device; or when a cellin which the UE is located changes, the second network side device maybe the same as or different from the first network side device.

It can be understood that when a network side device can simultaneouslymanage multiple cells, even if the cell of the UE changes, the UE may beon a same network side device. That is, in this case, a second networkside device on which the UE is located is the same as the first networkside device. This is not limited in the present disclosure.

This step is optional. That is, step 603 is directly performedregardless of whether a cell changes.

602. When the cell does not change, the UE sends an uplink schedulingrequest or a random access request to the second network side device, torequest an uplink resource from the second network side device, andsends uplink data to the second network side device according to theuplink resource.

If the cell does not change, according to a description in step 401, theUE still has the RRC connection to the first network side device (thesecond network side device), and the UE in the intermediate state maydirectly request the uplink resource from the first network side device,to send a buffer status report and/or the uplink data to the firstnetwork side device. Optionally, the UE keeps using the schedulingrequest or the random access request to request the uplink resource fromthe second network side device, and sends the uplink data to the secondnetwork side device according to the uplink resource.

Alternatively,

603. When the cell changes, the UE sends uplink data to the secondnetwork side device after the UE is restored to the connection state.

Specifically, if the cell changes, that is, when the first network sidedevice is different from the second network side device on which the UEis currently located, because the UE does not establish an RRCconnection to the second network side device, the UE first performs theforegoing steps 501 to 504; then sends an uplink scheduling request or arandom access request to the second network side device, to request anuplink resource from the second network side device; and sends theuplink data to the second network side device according to the uplinkresource. Alternatively, it is possible that after the UE is in theconnection state, the second network side device directly allocates anuplink resource to the UE. In this case, the UE does not need to send anuplink scheduling request or a random access request to the secondnetwork side device.

The following describes a specific implementation of data sending.

As shown in FIG. 7a -1 and FIG. 7a -2, when there is downlink data thatneeds to be received by UE from a network side device, the method mayfurther include the following steps.

701. When there is downlink data reaching a core network, a core networkdevice determines whether the core network device stores contextinformation of the UE in an intermediate state; and if the core networkdevice stores the context information of the UE in the intermediatestate, steps 702 to 709 are performed, or if the core network devicedoes not store the context information of the UE in the intermediatestate, steps 710 to 720 are performed.

Specifically, the context information of the UE in the intermediatestate may include at least one of the following:

indication information of the UE in the intermediate state, and a celllist or a network side device list information of the UE in theintermediate state.

When there is downlink data reaching a core network, a first networkside device may have already sent the context information of the UE inthe intermediate state to the core network device, and the core networkdevice confirms that the UE is in the intermediate state. It is alsopossible that there is downlink data reaching the core network devicebefore the first network side device sends the context information ofthe UE in the intermediate state to the core network device.Alternatively, a protocol or the core network device does not supportthe UE in the intermediate state, and certainly, there is no contextinformation of the UE in the intermediate state.

It can be understood that this step is optional. Specifically, the corenetwork device only determines whether the UE is in a connection stateor an idle state. If the UE is in the connection state, steps 710 to 720are performed. Alternatively, if the UE is in the idle state, a methodfor processing downlink data when UE is in the idle state in the priorart is performed. This is not limited in the present disclosure.

702. The core network device sends a paging message to at least onenetwork side device in a list.

Because the core network device confirms that the UE is in theintermediate state, the core network device learns that the UEestablishes an RRC connection to the first network side device. However,the core network device does not learn whether a cell of the UE changesor which cell the UE moves to. Therefore, the core network device needsto send a paging message to at least one network side device in thelist, to obtain a location of a cell in which the UE is currentlylocated.

Specifically, the paging message may include at least one of thefollowing information:

-   -   UE identification information, which may be all of or a part of        a temporary mobile subscriber identity (S-TMSI), or a C-RNTI;    -   information about some or all cells in the list; and    -   indication information of the UE in the intermediate state.

703. After receiving the paging message, the at least one network sidedevice sends the paging message to the UE in a cell respectivelycorresponding to the at least one network side device.

Specifically, at least one network side device sends, in a cell in alist included in the paging message or in a cell in a list included inobtained context information of the UE, the paging message to the UE.

704. After receiving the paging message, the UE determines whether acell in which the UE is located changes; and if the cell does notchange, step 705 is performed, or if the cell changes, step 707 isperformed.

This step is optional. That is, step 707 is performed regardless ofwhether the cell changes.

705. If the cell does not change, the UE sends a scheduling request or arandom access request to a first network side device, to request anuplink resource, and sends a buffer status report and/or a pagingresponse to the first network side device according to the uplinkresource.

706. The first network side device sends the paging response to the corenetwork device; then, go to step 709.

707. If the cell changes, the UE sends a buffer status report and/or apaging response to a second network side device after the UE is restoredto a connection state.

708. The second network side device sends the paging response to thecore network device.

Further, optionally, the second network side device may send a pathswitching request message to the core network device. The path switchingrequest message is used to request the core network device to switch adata channel from a path between the first network side device and thecore network device to a path between the second network side device andthe core network device, so that the core network learns that a networkside device of the serving cell in which the UE is currently located isthe second network side device.

Further, the core network device sends a path switching confirmationmessage to the second network side device. In this way, datatransmission can be performed between the UE, the second network sidedevice, and the core network device.

Further, optionally, after path switching, the second network sidedevice instructs the first network side device to release the contextinformation of the UE; or the core network device instructs the firstnetwork side device to release the context information of the UE.

Further, a network side device in a cell list of the first network sidedevice releases the context information of the UE.

709. The core network device sends the downlink data to the UE.

Specifically, the core network device first sends the downlink data to anetwork side device (for example, the network side device may be thefirst network side device, or may be the second network side device) ofa cell in which the UE is restored to an RRC connection. Then, thenetwork side device sends the downlink data to the UE.

710. The core network device sends the downlink data to a first networkside device on which a first cell of the UE is located.

The first network side device on which the first cell is located hereinis a network side device that sends configuration information includingthe list to the UE.

711. The first network side device on which the first cell is locatedsends a paging message to the UE.

712. The first network side device sends the paging message to at leastone second network side device in a list.

Specifically, the paging message is transmitted by using an X2interface, or is transmitted by using a core network device through anS1 interface. This is not limited in the present disclosure.

After receiving the paging message, the at least one second network sidedevice in the list sends the paging message to the UE. (This is similarto step 703.)

Further, optionally, the first network side device sends the downlinkdata to at least one second network side device in the list.

713. After receiving the paging message, the UE determines whether acell in which the UE is located changes; and if the cell does notchange, steps 714 and 715 are performed, or if the cell changes, step716 is performed.

This step is optional. That is, step 707 is performed regardless ofwhether the cell changes.

714. If the cell does not change, the UE sends a scheduling request or arandom access request to the first network side device, to request anuplink resource, and sends a buffer status report and/or a pagingresponse to the first network side device according to the uplinkresource.

715. The first network side device sends the downlink data to the UE.

Alternatively,

716. If the cell changes, the UE is restored to a connection state tothe second network side device.

Further, optionally, the UE sends a buffer status report and/or a pagingresponse to the second network side device.

717. After detecting that the UE is restored to the connection state,the second network side device notifies the first network side device.

This step is optional.

This step can be not performed when the first network side device andthe second network side device are a same device.

When the second network side device already receives data sent by thefirst network side device, step 718 is directly performed.

718. The first network side device sends the downlink data to the secondnetwork side device.

This step can be not performed when the first network side device andthe second network side device are a same device.

719. The second network side device sends the downlink data to the UE.

720. The first network side device and/or a device other than the secondnetwork side device to which the UE is restored to be connected releasescontext of the UE.

This step is optional.

As shown in FIG. 7b , another implementation is as follows: When a corenetwork device needs to transmit downlink data to UE, the core networkdevice only determines whether the UE is in a connection state or anidle state, and if the UE is in the connection state, the followingsteps are performed.

721. The core network device sends downlink data to a network sidedevice on which a first cell of the UE is located.

When the core network device determines that the core network devicedoes not store context information of the UE in an intermediate state,the UE may be in an idle state; or may be in the intermediate state butthe network side device has not sent the context information of the UEin the intermediate state to the core network device; or may be in aconnection state. If the UE is in the idle state and needs to transmitdownlink data, a method the same as that in the prior art is performed.If the UE is in the intermediate state and needs to send downlink data,the core network device first sends the downlink data to the networkside device on which the first cell of the UE is located. In this case,a network side device on which a current serving cell of the UE islocated may be a first network side device before the cell of the UEchanges, or may be a second network side device when the cell of the UEchanges.

723. The network side device on which the first cell is locateddetermines whether the UE is in an RRC connection state and/or an RRCintermediate state; then, go to step 724 or step 725.

724. If the UE is in the RRC connection state, the network side deviceon which the first cell is located sends the downlink data to the UE.

725. If the UE is not in the RRC connection state, a network side deviceon which a current serving cell of the UE is located sends a pagingmessage to the UE.

The paging message may include context information of the UE. Then,steps 704 to 709 may be performed.

In the embodiments of the present disclosure, for example, when a cellin which the UE is located does not change, the second network sidedevice is the same as the first network side device. When a cell inwhich the UE is located changes, the second network side device may bedifferent from the first network side device.

It can be understood that when a network side device can simultaneouslymanage multiple cells, even if the cell of the UE changes, the UE may beon a same network side device. That is, in this case, a second networkside device on which the UE is located is the same as the first networkside device. This is not limited in the present disclosure.

By using the foregoing descriptions, a comparison of downlink dataprocessing in a core network in the embodiments of the presentdisclosure and that in the prior art may be shown in table 1. Table 1shows different method for processing downlink data by a network sidedevice.

TABLE 1 Processing Processing performed by Actual Core Downlink dataperformed by second state of network processing in a first networknetwork side Case UE state core network side device device 1 ConnectionConnection Page-in the prior Page-in the Page-in the state state artprior art prior art 2 Intermediate Connection Send the Page the UE Pagethe UE; state state downlink data to and send a notify the first thefirst network paging message network side side device to the seconddevice after a network side connection is device; and restored; anddirectly send send the data to the data to the the UE UE according to apaging result, or send the data to the UE by using the second networkside device 3 Send the Page UE, and Page UE; and downlink data to send apaging send the data to the first network message to the the UE after aside device second network connection is side device; restored send thedata to the second network side device; and send the data to the UEaccording to a paging result 4 Intermediate Intermediate Page the UEPage the UE, Page the UE, state state inside a first and feed back a andfeed back a network side paging paging response device and a responsesecond network side device in a list; send, according to a pagingresult, data to a network side device to which the UE is restored to beconnected 5 Directly send the Page the UE, Page the UE, data to a firstsend the data to send the data to network side the UE, and the UE, anddevice and a feed back a feed back a second network paging pagingresponse side device in a response list

This embodiment of the present disclosure provides a signalingoptimization method. When UE establishes a connection to a network sidedevice to be in a connection state, if configuration information sent bythe network side device is received and the configuration informationincludes a cell list or a base station list, the UE switches from theconnection state to an intermediate state when the UE stores contextinformation of the UE. The intermediate state means that if the UE movesand a cell movement range falls within the list, the UE performs cellreselection without a need to notify the network side device. If the UEin the intermediate state needs to be restored to the connection statebecause there is data that needs to be transmitted or a TAU needs to beperformed, the UE does not need to establish the context information ofthe UE with a network side. In comparison with a case in which the UEswitches from an idle state to the connection state, signaling isreduced, a data transmission delay of the UE is shortened, and a problemof heavy signaling overheads and a long data transmission delay when theUE accesses the network side is resolved.

An embodiment of the present disclosure provides user equipment 80. Asshown in FIG. 8, the user equipment 80 includes:

a receiving unit 801, configured to receive configuration informationsent by a first network side device, where the configuration informationincludes a list, and the list is a cell list or a base station list; and

a processing unit 802, configured to enter an intermediate stateaccording to the configuration information, where the intermediate statemeans that: when the UE stores context information of the UE, if the UEmoves and a cell movement range falls within a coverage area of a cellor a base station included in the list, the UE performs cell reselectionaccording to the list.

Optionally, the intermediate state further means that: if the cellmovement range of the UE falls beyond the coverage area of the cell orthe base station included in the list, the UE sends a notificationmessage to a network side device on which a current serving cell of theUE is located, so that the UE is restored from the intermediate state toa connection state or returns to an idle state, and the network sidedevice on which the current serving cell is located is the first networkside device or a second network side device after the UE performs cellreselection.

Optionally, the configuration information further includes a conditionunder which the first network side device instructs the UE to enter theintermediate state according to the configuration information, and thecondition includes entering the intermediate state immediately orentering the idle state after a preset time; and/or

the configuration information further includes a time period in whichthe first network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

Optionally, the configuration information further includes a cellreselection parameter for performing cell reselection by the UE.

Optionally, the configuration information is carried in a radio resourcecontrol (RRC) message by the first network side device, and the RRCmessage includes an RRC connection establishment message, an RRCreconfiguration message, or an RRC connection release message.

Optionally, in a process in which the processing unit 802 is configuredto perform cell reselection, when it is determined that the UE needs tosend uplink data to a network side and/or needs to receive downlink datafrom the network side, the processing unit 802 is further configured torestore the UE 80 to the connection state.

The UE 80 further includes: a sending unit 803, configured to send theuplink data to a network side device that has been restored to theconnection state; and/or the receiving unit is configured to receive thedownlink data from the network side device that has been restored to theconnection state. The network side device that has been restored to theconnection state includes the first network side device or the secondnetwork side device.

Optionally, the processing unit 802 may be specifically configured to:

if the cell of the UE does not change, send a scheduling request or arandom access request to the first network side device by using thesending unit 803, to restore the UE 80 to the connection state.

Optionally, the sending unit 803 may be further configured to send anRRC resume request message to the first network side device or thesecond network side device.

The RRC resume confirmation message is used to instruct the UE to berestored to the connection state.

The receiving unit 801 may be further configured to receive an RRCresume confirmation message sent by the first network side device or thesecond network side device. The RRC resume confirmation message includesa parameter for extending, deleting, or modifying the contextinformation of the UE by the first network side device or the secondnetwork side device.

The sending unit 803 may be further configured to send an RRC connectionresume completion message to the first network side device or the secondnetwork side device.

This embodiment of the present disclosure provides user equipment. Theuser equipment is configured to: receive configuration information sentby a first network side device, where the configuration informationincludes a list, and the list is a cell list or a base station list; andenter an intermediate state according to the configuration information,where the intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in the list,the UE performs cell reselection according to the list. In this way, acell handover is not performed when a cell of the UE changes. Instead,cell reselection is performed when the UE stores the contextinformation, so as to reduce signaling overheads of the UE and a networkside, and shorten a data transmission delay.

An embodiment of the present disclosure provides a first network sidedevice 90. As shown in FIG. 9, the first network side device 90includes:

a sending unit 901, configured to send configuration information to auser equipment (UE), where the configuration information includes alist, the list is a cell list or a base station list, the configurationinformation is used to instruct the UE to enter an intermediate state,and the intermediate state means that when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in the list,the UE performs cell reselection according to the list.

The sending unit 901 is further configured to send the contextinformation of the UE to a network side device in the list.

Optionally, the configuration information is further used to indicatethat after the UE enters the intermediate state, if the UE moves and thecell movement range falls beyond the coverage area of the cell or thebase station included in the list, the UE sends a notification messageto a network side device on which a current serving cell of the UE islocated, so that the UE is restored from the intermediate state to aconnection state or returns to an idle state, and the network sidedevice on which the current serving cell is located is the first networkside device or a second network side device after the UE performs cellreselection.

Optionally, the configuration information further includes a conditionunder which the first network side device instructs the UE to enter theintermediate state according to the configuration information, and thecondition includes entering the intermediate state immediately orentering the intermediate state after a preset time; and/or

the configuration information further includes a time period in whichthe first network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

Optionally, the configuration information further includes a cellreselection parameter for performing cell reselection by the UE.

Optionally, the sending unit 901 may be specifically configured to:

send the configuration information to the UE by using a radio resourcecontrol (RRC) message, where the RRC message includes an RRCreconfiguration message or an RRC connection release message.

Optionally, the sending unit 901 may be further configured to send thecontext information of the UE to a core network device.

The first network side device 90 may further include: a processing unit902, configured to release the context information of the UE when thefirst network side device 90 stores the context information of the UEfor a preset time.

Optionally, the first network side device 90 may further include areceiving unit 903, configured to receive an RRC resume request messagesent by the UE. The RRC resume request message includes at least one ofcell information of the first network side device, a cell radio networktemporary identity (C-RNTI) of the UE, or indication information forrequesting to restore the UE to the connection state.

The sending unit 901 is further configured to send an RRC resumeconfirmation message to the UE. The RRC resume confirmation messageincludes a parameter for extending, deleting, or modifying the contextinformation of the UE by the first network side device.

The receiving unit 903 may be further configured to receive an RRCconnection resume completion message sent by the UE.

Optionally, the receiving unit 903 is further configured to receive anuplink scheduling request or a random access request sent by the UE.

The sending unit 901 is further configured to send an uplink resource tothe UE. The uplink resource is used by the UE to send uplink data to thefirst network side device or to receive downlink data from the firstnetwork side device according to the uplink resource.

This embodiment of the present disclosure provides a first network sidedevice. The first network side device is configured to: sendconfiguration information to a user equipment (UE), where theconfiguration information includes a list, the list is a cell list or abase station list, the configuration information is used to instruct theUE to enter an intermediate state, and the intermediate state meansthat: when the UE stores context information of the UE, if the UE movesand a cell movement range falls within a coverage area of a cell or abase station included in the list, the UE performs cell reselectionaccording to the list; and further send the context information of theUE to a network side device in the list. In this way, a cell handover isnot performed when a cell of the UE in the intermediate state changes.Instead, a cell reselection process is performed, so as to reducesignaling overheads of the UE and a network side, and shorten a datatransmission delay.

An embodiment of the present disclosure provides user equipment 100. Asshown in FIG. 10, the user equipment 100 includes a bus 1001, and atransmitter 1003, a receiver 1004, a processor 1002, and a memory 1005that are connected to the bus 1001. The memory 1005 is configured tostore an instruction and data. The receiver 1004 executes theinstruction, to receive configuration information sent by a firstnetwork side device. The configuration information includes a list. Thelist is a cell list or a base station list. The processor 1002 executesthe instruction, to enter an intermediate state according to theconfiguration information. The intermediate state means that: when theUE stores context information of the UE, if the UE moves and a cellmovement range falls within a coverage area of a cell or a base stationincluded in the list, the UE performs cell reselection according to thelist.

In this embodiment of the present disclosure, optionally, theintermediate state further means that: if the cell movement range of theUE falls beyond the coverage area of the cell or the base stationincluded in the list, the UE sends a notification message to a networkside device on which a current serving cell of the UE is located, sothat the UE is restored from the intermediate state to a connectionstate or returns to an idle state. The network side device on which thecurrent serving cell is located is the first network side device or asecond network side device after the UE performs cell reselection.

In this embodiment of the present disclosure, optionally, theconfiguration information further includes a condition under which thefirst network side device instructs the UE to enter the intermediatestate according to the configuration information, and the conditionincludes entering the intermediate state immediately or entering theidle state after a preset time; and/or

the configuration information further includes a time period in whichthe first network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

In this embodiment of the present disclosure, optionally, theconfiguration information further includes a cell reselection parameterfor performing cell reselection by the UE.

In this embodiment of the present disclosure, optionally, theconfiguration information is carried in a radio resource control (RRC)message by the first network side device, and the RRC message includesan RRC connection establishment message, an RRC reconfiguration message,or an RRC connection release message.

In this embodiment of the present disclosure, optionally, in a processin which the processor 1002 executes the instruction to perform cellreselection, when it is determined that the UE 100 needs to send uplinkdata to a network side and/or needs to receive downlink data from thenetwork side, the processor 1002 is further configured to restore the UE100 to the connection state.

The transmitter 1003 executes the instruction to send the uplink data toa network side device that has been restored to the connection state;and/or the receiver 1004 is configured to receive the downlink data fromthe network side device that has been restored to the connection state.The network side device that has been restored to the connection stateincludes the first network side device or the second network sidedevice.

In this embodiment of the present disclosure, optionally, thetransmitter 1003 executes the instruction to:

if the cell of the UE does not change, send a scheduling request or arandom access request to the first network side device, to restore theUE 100 to the connection state.

In this embodiment of the present disclosure, optionally, thetransmitter 1003 executes the instruction to further send an RRC resumerequest message to the first network side device or the second networkside device. The RRC resume request message includes at least one ofcell information of the first network side device, a cell radio networktemporary identity (C-RNTI) of the UE, or indication information forrequesting to restore the UE to the connection state.

The receiver 1004 executes the instruction to further receive an RRCresume confirmation message sent by the first network side device or thesecond network side device. The RRC resume confirmation message is usedto indicate that the UE is restored to the connection state.

The transmitter 1003 executes the instruction to further send an RRCconnection resume completion message to the first network side device orthe second network side device.

This embodiment of the present disclosure provides user equipment. Theuser equipment is configured to: receive configuration information sentby a first network side device, where the configuration informationincludes a list, and the list is a cell list or a base station list; andenter an intermediate state according to the configuration information,where the intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in the list,the UE performs cell reselection according to the list. In this way, acell handover is not performed when a cell of the UE changes. Instead,cell reselection is performed when the UE stores the contextinformation, so as to reduce signaling overheads of the UE and a networkside, and shorten a data transmission delay.

An embodiment of the present disclosure provides a first network sidedevice 110. As shown in FIG. 11, the first network side device 110includes a bus 1101, and a transmitter 1103, a receiver 1104, aprocessor 1102, and a memory 1105 that are connected to the bus 1101.The memory 1105 is configured to store an instruction and data. Thetransmitter 1103 executes the instruction to send configurationinformation to a user equipment (UE). The configuration informationincludes a list. The list is a cell list or a base station list. Theconfiguration information is used to instruct the UE to enter anintermediate state, and the intermediate state means that: when the UEstores context information of the UE, if the UE moves and a cellmovement range falls within a coverage area of a cell or a base stationincluded in the list, the UE performs cell reselection according to thelist. The transmitter 1103 executes the instruction to further send thecontext information of the UE to a network side device in the list.

In this embodiment of the present disclosure, optionally, theconfiguration information is further used to indicate that after the UEenters the intermediate state, if the UE moves and the cell movementrange falls beyond the coverage area of the cell or the base stationincluded in the list, the UE sends a notification message to a networkside device on which a current serving cell of the UE is located, sothat the UE is restored from the intermediate state to a connectionstate or returns to an idle state. The network side device on which thecurrent serving cell is located is the first network side device or asecond network side device after the UE performs cell reselection.

In this embodiment of the present disclosure, optionally, theconfiguration information further includes a condition under which thefirst network side device instructs the UE to enter the intermediatestate according to the configuration information, and the conditionincludes entering the intermediate state immediately or entering theintermediate state after a preset time; and/or

the configuration information further includes a time period in whichthe first network side device instructs the UE to enter the intermediatestate according to the configuration information, and/or an operationinstruction performed after the UE enters the intermediate state duringthe time period according to the configuration information, and theoperation instruction is used to instruct the UE to enter the idle stateand/or instruct the UE to notify the first network side device ofcurrent location information of the UE.

In this embodiment of the present disclosure, optionally, theconfiguration information further includes a cell reselection parameterfor performing cell reselection by the UE.

In this embodiment of the present disclosure, optionally, thetransmitter 1103 may execute the instruction to specifically:

send the configuration information to the UE by using a radio resourcecontrol (RRC) message, where the RRC message includes an RRCreconfiguration message or an RRC connection release message.

In this embodiment of the present disclosure, optionally, thetransmitter 1103 may execute the instruction to further send the contextinformation of the UE to a core network device.

The processor 1102 executes the instruction to release the contextinformation of the UE when the first network side device 110 stores thecontext information of the UE for a preset time.

In this embodiment of the present disclosure, optionally, the receiver1104 executes the instruction to receive an RRC resume request messagesent by the UE. The RRC resume request message includes at least one ofcell information of the first network side device, a cell radio networktemporary identity (C-RNTI) of the UE, or indication information forrequesting to restore the UE to the connection state.

The transmitter 1103 may execute the instruction to further send an RRCresume confirmation message to the UE. The RRC resume confirmationmessage includes a parameter for extending, deleting, or modifying thecontext information of the UE by the first network side device.

The receiver 1104 may execute the instruction to further receive an RRCconnection resume completion message sent by the UE.

In this embodiment of the present disclosure, optionally, the receiver1104 may execute the instruction to further receive an uplink schedulingrequest or a random access request sent by the UE.

The transmitter 1103 executes the instruction to further send an uplinkresource to the UE. The uplink resource is used by the UE to send uplinkdata to the first network side device or to receive downlink data fromthe first network side device according to the uplink resource.

Therefore, this embodiment of the present disclosure provides a firstnetwork side device. The first network side device is configured to:send configuration information to a user equipment (UE), where theconfiguration information includes a list, the list is a cell list or abase station list, the configuration information is used to instruct theUE to enter an intermediate state, and the intermediate state meansthat: when the UE stores context information of the UE, if the UE movesand a cell movement range falls within a coverage area of a cell or abase station included in the list, the UE performs cell reselectionaccording to the list; and further send the context information of theUE to a network side device in the list. In this way, a cell handover isnot performed if a cell of the UE in the intermediate state changes.Instead, a cell reselection process is performed, so as to reducesignaling overheads of the UE and a network side, and shorten a datatransmission delay.

An embodiment of the present disclosure provides a second network sidedevice 120. As shown in FIG. 12, the second network side device 120includes:

a receiving unit 1201, configured to receive indication information of auser equipment (UE) in an intermediate state that is sent by a firstnetwork side device, where the intermediate state means that: when theUE stores context information of the UE, if the UE moves and a cellmovement range falls within a coverage area of a cell or a base stationincluded in a list sent by the first network side device, the UEperforms cell reselection according to the list; and

an obtaining unit 1202, configured to obtain the context information ofthe UE from the first network side device, or obtain the contextinformation of the UE from the second network side device when a radioresource control (RRC) resume request message sent by the UE isreceived, so as to receive uplink data from the UE or send downlink datato the UE.

The second network side device may be a network side device that isobtained after the UE performs cell reselection and on which a cell islocated.

Optionally, the receiving unit 1201 may be configured to receive andsave context information of the UE that is sent by the first networkside device.

Optionally, the obtaining unit 1202 may be specifically configured to:

if the second network side device does locally store the contextinformation of the UE before the second network side device receives theRRC resume request message sent by the UE, obtain the contextinformation of the UE from the second network side device; or if thesecond network side device does not locally store the contextinformation of the UE before the second network side device receives theRRC resume request message sent by the UE, obtain the contextinformation of the UE from the first network side device.

The RRC resume request message is used to be sent to the second networkside device when the UE is restored from the intermediate state to aconnection state.

Optionally, the second network side device 120 further includes: asending unit 1203, configured to: when the second network side devicereceives a paging message sent by a core network device and determinesthat there is the downlink data that needs to be sent to the UE, sendthe paging message to the UE, and after the second network side deviceestablishes an RRC connection to the UE, send, to the UE, the downlinkdata received from the core network device.

Alternatively, the sending unit 1203 is further configured to: when apaging message sent by the first network side device is received and itis determined that there is the downlink data that needs to be sent tothe UE, send the paging message to the UE, and after the second networkside device establishes an RRC connection to the UE, send, to the UE,the downlink data received from the first network side device.

This embodiment of the present disclosure provides a second network sidedevice. The second network side device receives indication informationof UE in an intermediate state that is sent by a first network sidedevice. Therefore, when a network side device on which a current servingcell of the UE is located is the second network side device, the secondnetwork side device may not execute a process of establishing contextinformation of the UE with the UE. Instead, The second network sidedevice directly obtains the context information of the UE from thesecond network side device or from the first network side device, so asto reduce signaling overheads of the UE and a network side, and shortena data transmission delay.

An embodiment of the present disclosure further provides a core networkdevice 130. As shown in FIG. 13, the core network device 130 includes:

a receiving unit 1301, configured to receive indication information of auser equipment (UE) in an intermediate state that is sent by the UE,where the intermediate state means that: when the UE stores contextinformation of the UE, if the UE moves and a cell movement range fallswithin a coverage area of a cell or a base station included in a listsent by a first network side device to the UE, the UE performs cellreselection according to the list; and

a sending unit 1302, configured to: if the core network device needs totransmit downlink data to the UE, send a paging message to at least onenetwork side device in the list, to send the downlink data to the UE byusing a first network side device or a second network side device thatis in the at least one network side device and that is connected to theUE; or send the downlink data to the first network side device, to sendthe downlink data to the UE by using the first network side device; orsend the downlink data to at least one network side device in the list,to send the downlink data to the UE by using the at least one networkside device.

Optionally, the receiving unit 1301 is further configured to receive andsave context information of the UE that is sent by the first networkside device.

This embodiment of the present disclosure provides a core networkdevice. The core network device receives indication information of auser equipment (UE) in an intermediate state that is sent by the UE. Inthis way, when transmitting downlink data to the UE, the core networkdevice may send a paging message to a network side device in a list, tosend the downlink data to the UE by using a network side device thatreceives the paging message and that has an RRC connection to the UE; ordirectly send the downlink data to a first network side device, and sendthe downlink data to the UE by using the first network side device, soas to reduce signaling overheads of the UE and a network side, andshorten a data transmission delay.

An embodiment of the present disclosure provides a second network sidedevice 140. As shown in FIG. 14, the second network side device 140includes a bus 1401, and a transmitter 1403, a receiver 1404, aprocessor 1402, and a memory 1405 that are connected to the bus 1401.The memory 1405 is configured to store an instruction and data. Thereceiver 1404 executes the instruction to receive indication informationof a user equipment (UE) in an intermediate state that is sent by afirst network side device. The intermediate state means that: when theUE stores context information of the UE, if the UE moves and a cellmovement range falls within a coverage area of a cell or a base stationincluded in a list sent by the first network side device, the UEperforms cell reselection according to the list. The processor 1402 isconfigured to obtain the context information of the UE from the firstnetwork side device, or obtain the context information of the UE fromthe second network side device when the receiver receives a radioresource control (RRC) resume request message sent by the UE, so as toreceive uplink data from the UE or send downlink data to the UE.

In this embodiment of the present disclosure, optionally, the receiver1404 is further configured to receive and save context information ofthe UE that is sent by the first network side device.

In this embodiment of the present disclosure, optionally, the processor1402 is specifically configured to: if the memory 1405 stores thecontext information of the UE when the receiver 1404 receives the radioresource control (RRC) resume request message sent by the UE, obtain thecontext information of the UE from the memory 1405; or if the memory1405 does not store the context information of the UE before thereceiver 1404 receives the RRC resume request message sent by the UE,obtain the context information of the UE from the first network sidedevice.

The RRC resume request message is used to be sent to the second networkside device when the UE is restored from the intermediate state to aconnection state.

In this embodiment of the present disclosure, optionally, thetransmitter 1403 is configured to: when the second network side devicereceives a paging message sent by a core network device and determinesthat there is the downlink data that needs to be sent to the UE, sendthe paging message to the UE, and after the second network side deviceestablishes an RRC connection to the UE, send, to the UE, the downlinkdata received from the core network device; or

the transmitter 1403 is configured to: when a paging message sent by thefirst network side device is received and it is determined that there isthe downlink data that needs to be sent to the UE, send the pagingmessage to the UE, and after the second network side device establishesan RRC connection to the UE, send, to the UE, the downlink data receivedfrom the first network side device.

This embodiment of the present disclosure provides a second network sidedevice. The second network side device receives indication informationof UE in an intermediate state that is sent by a first network sidedevice. Therefore, when a network side device on which a current servingcell of the UE is located is the second network side device, the secondnetwork side device may not execute a process of establishing contextinformation of the UE with the UE. Instead, the second network sidedevice directly obtains the context information of the UE from thesecond network side device or from the first network side device, so asto reduce signaling overheads of the UE and a network side, and shortena data transmission delay.

An embodiment of the present disclosure provides a core network device150. As shown in FIG. 15, the core network device 150 includes a bus1501, and a transmitter 1503, a receiver 1504, a processor 1502, and amemory 1505 that are connected to the bus 1501. The memory 1505 isconfigured to store an instruction and data. The receiver 1504 isconfigured to receive indication information of a user equipment (UE) inan intermediate state that is sent by the UE. The intermediate statemeans that: when the UE stores context information of the UE, if the UEmoves and a cell movement range falls within a coverage area of a cellor a base station included in a list sent by a first network side deviceto the UE, the UE performs cell reselection according to the list.

The transmitter 1503 is configured to: if the core network device needsto transmit downlink data to the UE, send a paging message to at leastone network side device in the list, to send the downlink data to the UEby using a first network side device or a second network side devicethat is in the at least one network side device and that is connected tothe UE; or send the downlink data to the first network side device, tosend the downlink data to the UE by using the first network side device;or send the downlink data to at least one network side device in thelist, to send the downlink data to the UE by using the at least onenetwork side device.

Optionally, the receiver 1504 is further configured to receive and savecontext information of the UE that is sent by the first network sidedevice.

This embodiment of the present disclosure provides a core networkdevice. The core network device receives indication information of auser equipment (UE) in an intermediate state that is sent by the UE. Inthis way, when transmitting downlink data to the

UE, the core network device may send a paging message to a network sidedevice in a list, to send the downlink data to the UE by using a networkside device that receives the paging message and that has an RRCconnection to the UE; or directly send the downlink data to a firstnetwork side device, and send the downlink data to the UE by using thefirst network side device, so as to reduce signaling overheads of the UEand a network side, and shorten a data transmission delay.

In the several embodiments provided in this application, it should beunderstood that the disclosed device and method may be implemented inother manners. For example, the described device embodiment is merely anexample. For example, the unit division is merely logical functiondivision and may be other division in actual implementation. Forexample, multiple units or components may be combined or integrated intoanother system, or some features may be ignored or not performed. Inaddition, the displayed or discussed mutual couplings or directcouplings or communication connections may be implemented through someinterfaces, indirect couplings or communication connections between theapparatuses or units, or electrical connections, mechanical connections,or connections in other forms.

In addition, functional units in the devices and systems in theembodiments of the present disclosure may be integrated into oneprocessing unit, or each of the units may exist alone physically, or twoor more units are integrated into one unit. The units may be implementedin a form of hardware, or may be implemented in a form of hardware inaddition to a software functional unit.

All or some of the steps of the method embodiments may be implemented bya program instructing relevant hardware. The program may be stored in acomputer-readable storage medium. When the program runs, the steps ofthe method embodiments are performed. The foregoing storage mediumincludes: any medium that can store program code, such as a USB flashdrive, a removable hard disk, a read-only memory (ROM), a random accessmemory (RAM), a magnetic disk, or an optical disc.

The foregoing descriptions are merely specific implementations of thepresent disclosure, but are not intended to limit the protection scopeof the present disclosure. Any variation or replacement readily figuredout by persons skilled in the art within the technical scope disclosedin the present disclosure shall fall within the protection scope of thepresent disclosure. Therefore, the protection scope of the presentdisclosure shall be subject to the protection scope of the claims.

1. A user equipment (UE), comprising: a receiver, configured to receive configuration information sent by a first network side device, wherein the configuration information comprises a list, and the list is a cell list or a base station list; and a processor, configured to cause the UE enter an intermediate state according to the configuration information, wherein the intermediate state is a state such that when the UE moves and a cell movement range falls within a coverage area of a cell or a base station comprised in the list, the UE performs cell reselection according to the list.
 2. The UE according to claim 1, wherein when the UE is in the intermediate state, if the cell movement range of the UE falls beyond the coverage area of the cell or the base station comprised in the list, then the UE sends a notification message to a network side device on which a current serving cell of the UE is located, so that the UE is restored from the intermediate state to a connection state or returns to an idle state, and the network side device on which the current serving cell is located is the first network side device or a second network side device after the UE performs cell reselection.
 3. The UE according to claim 1, wherein the configuration information further comprises one or more of: a condition under which the first network side device instructs the UE to enter the intermediate state according to the configuration information, and the condition comprises entering the intermediate state immediately or entering an idle state after a preset time; a time period in which the first network side device instructs the UE to enter the intermediate state according to the configuration information; and an operation instruction performed after the UE enters the intermediate state during the time period according to the configuration information, wherein the operation instruction is used to instruct the UE to enter the idle state and/or instruct the UE to notify the first network side device of current location information of the UE.
 4. The UE according to claim 1, wherein the configuration information further comprises a cell reselection parameter for performing cell reselection by the UE.
 5. The UE according to claim 1, wherein the configuration information is carried in a radio resource control (RRC) message by the first network side device, and the RRC message comprises an RRC connection establishment message, an RRC reconfiguration message, or an RRC connection release message.
 6. The UE according to claim 1, wherein in a process in which the processor is configured to perform cell reselection, when it is determined that the UE needs to send uplink data to a network side from the network side, the processor is further configured to restore the UE to the connection state; and wherein the UE further comprises: a transmitter, configured to send the uplink data to a network side device that has been restored to the connection state, wherein the network side device that has been restored to the connection state comprises the first network side device or the second network side device.
 7. The UE according to claim 6, wherein the transmitter is further configured to: send a scheduling request or a random access request to the first network side device when the cell of the UE does not change, to restore the UE to the connection state.
 8. The UE according to claim 6, wherein: the transmitter is further configured to send a radio resource control (RRC) resume request message to the first network side device or the second network side device, wherein the RRC resume request message comprises at least one of cell information of the first network side device, a cell radio network temporary identity (C-RNTI) of the UE, or indication information for requesting to restore the UE to the connection state; the receiver is further configured to receive an RRC resume confirmation message sent by the first network side device or the second network side device, wherein the RRC resume confirmation message is used to indicate that the UE is restored to the connection state; and the transmitter is further configured to send an RRC connection resume completion message to the first network side device or the second network side device.
 9. A first network side device, comprising: a transmitter, configured to send configuration information to a user equipment (UE), wherein the configuration information comprises a list, wherein the list is a cell list or a base station list, wherein the configuration information is used to instruct the UE to enter an intermediate state, and wherein the intermediate state is a state that, when the UE stores context information of the UE, if the UE moves and a cell movement range falls within a coverage area of a cell or a base station comprised in the list, then the UE performs cell reselection according to the list, wherein the transmitter is further configured to send the context information of the UE to a network side device in the list.
 10. The first network side device according to claim 9, wherein the configuration information is further used to indicate that: after the UE enters the intermediate state, if the UE moves and the cell movement range falls beyond the coverage area of the cell or the base station comprised in the list, the UE sends a notification message to a network side device on which a current serving cell of the UE is located, so that the UE is restored from the intermediate state to a connection state or returns to an idle state, and the network side device on which the current serving cell is located is the first network side device or a second network side device after the UE performs cell reselection.
 11. The first network side device according to claim 9, wherein the configuration information further comprises one or more of: a condition under which the first network side device instructs the UE to enter the intermediate state according to the configuration information, and the condition comprises entering the intermediate state immediately or entering the intermediate state after a preset time; a time period in which the first network side device instructs the UE to enter the intermediate state according to the configuration information; and an operation instruction performed after the UE enters the intermediate state during the time period according to the configuration information, and the operation instruction is used to instruct the UE to enter an idle state and/or instruct the UE to notify the first network side device of current location information of the UE.
 12. The first network side device according to claim 9, wherein the configuration information further comprises a cell reselection parameter for performing cell reselection by the UE.
 13. The first network side device according to claim 9, wherein the transmitter is further configured to: send the configuration information to the UE by using a radio resource control (RRC) message, wherein the RRC message comprises an RRC reconfiguration message or an RRC connection release message.
 14. The first network side device according to claim 9, wherein the transmitter is further configured to send the context information of the UE to a core network device; and the first network side device further comprises: a processor, configured to release the context information of the UE when the first network side device stores the context information of the UE for a preset time.
 15. The first network side device according to claim 9, further comprising: a receiver, configured to receive a radio resource control (RRC) resume request message sent by the UE, wherein the RRC resume request message comprises at least one of cell information of the first network side device, a cell radio network temporary identity (C-RNTI) of the UE, or indication information for requesting to restore the UE to the connection state, wherein: the transmitter is further configured to send an RRC resume confirmation message to the UE, wherein the RRC resume confirmation message comprises a parameter for extending, deleting, or modifying the context information of the UE by the first network side device; and the receiver is further configured to receive an RRC connection resume completion message sent by the UE.
 16. The first network side device according to claim 9, wherein the receiver is further configured to receive an uplink scheduling request or a random access request sent by the UE; and the transmitter is further configured to send an uplink resource to the UE, wherein the uplink resource is used by the UE to send uplink data to the first network side device or to receive downlink data from the first network side device according to the uplink resource.
 17. A second network side device, comprising: a receiver, configured to receive indication information of a user equipment (UE) in an intermediate state that is sent by a first network side device, wherein the intermediate state is a state that, when the UE stores context information of the UE, if the UE moves and a cell movement range falls within a coverage area of a cell or a base station comprised in a list sent by the first network side device, then the UE performs cell reselection according to the list; and a processor, configured to obtain the context information of the UE from the first network side device, or obtain the context information of the UE from the second network side device when the receiver receives a radio resource control (RRC) resume request message sent by the UE, so as to receive uplink data from the UE or send downlink data to the UE.
 18. The second network side device according to claim 17, wherein the receiver is further configured to receive and save context information of the UE that is sent by the first network side device.
 19. The second network side device according to claim 17, wherein the RRC resume request message is sent by the UE to the second network side device when the UE is restored from the intermediate state to a connection state, and wherein the processor is further configured to: if a memory stores the context information of the UE when the receiver receives the RRC resume request message sent by the UE, obtain the context information of the UE from the memory; or if a memory does not store the context information of the UE before the receiver receives the RRC resume request message sent by the UE, obtain the context information of the UE from the first network side device.
 20. The second network side device according to claim 17, wherein the second network side device further comprises: a transmitter, configured to: when the second network side device receives a paging message sent by a core network device and determines that there is the downlink data that needs to be sent to the UE, send the paging message to the UE, and after the second network side device establishes an RRC connection to the UE, send, to the UE, the downlink data received from the core network device; or when a paging message sent by the first network side device is received and it is determined that there is the downlink data that needs to be sent to the UE, send the paging message to the UE, and after the second network side device establishes an RRC connection to the UE, send, to the UE, the downlink data received from the first network side device.
 21. The UE according to claim 1, wherein in a process in which the processor is configured to perform cell reselection, when it is determined that the UE needs to receive downlink data from the network side, the processor is further configured to restore the UE to the connection state; and wherein the receiver is configured to receive the downlink data from the network side device that has been restored to the connection state, wherein the network side device that has been restored to the connection state comprises the first network side device or the second network side device. 